# AOSP Presubmit Hooks

[TOC]

This repo holds hooks that get run by repo during the upload phase.  They
perform various checks automatically such as running linters on your code.

Note: Currently all hooks are disabled by default.  Each repo must explicitly
turn on any hook it wishes to enforce.

## Usage

Normally these execute automatically when you run `repo upload`.  If you want to
run them by hand, you can execute `pre-upload.py` directly.  By default, that
will scan the active repo and process all commits that haven't yet been merged.
See its help for more info.

### Bypassing

Sometimes you might want to bypass the upload checks.  While this is **strongly
discouraged** (often failures you add will affect others and block them too),
sometimes there are valid reasons for this.  You can simply use the option
`--no-verify` when running `repo upload` to skip all upload checks.  This will
skip **all** checks and not just specific ones.  It should be used only after
having run & evaluated the upload output previously.

# Config Files

There are two types of config files:
* Repo project-wide settings (e.g. all of AOSP).  These set up defaults for all
  projects that are checked out via a single manifest.
* Project-local settings (e.g. a single .git repo).  These control settings for
  the local project you're working on.

The merging of these config files control the hooks/checks that get run when
running `repo upload`.

## GLOBAL-PREUPLOAD.cfg

These are the manifest-wide defaults and can be located in two places:
* `.repo/manifests/GLOBAL-PREUPLOAD.cfg`: The manifest git repo.
  Simply check this in to the manifest git repo and you're done.
* `GLOBAL-PREUPLOAD.cfg`: The top level of the repo checkout.
  For manifests that don't have a project checked out at the top level,
  you can use repo's `<copyfile>` directive.

These config files will be loaded first before stacking `PREUPLOAD.cfg`
settings on top.

## PREUPLOAD.cfg

This file are checked in the top of a specific git repository.  Stacking them
in subdirectories (to try and override parent settings) is not supported.

## Example

```
[Options]
ignore_merged_commits = true

[Hook Scripts]
name = script --with args ${PREUPLOAD_FILES}

[Builtin Hooks]
cpplint = true

[Builtin Hooks Options]
cpplint = --filter=-x ${PREUPLOAD_FILES}

[Tool Paths]
clang-format = /usr/bin/clang-format
```

## Environment

Hooks are executed in the top directory of the git repository.  All paths should
generally be relative to that point.

A few environment variables are set so scripts don't need to discover things.

* `REPO_PROJECT`: The name of the project.
   e.g. `platform/tools/repohooks`
* `REPO_PATH`: The path to the project relative to the root.
   e.g. `tools/repohooks`
* `REPO_REMOTE`: The name of the git remote.
   e.g. `aosp`.
* `REPO_LREV`: The name of the remote revision, translated to a local tracking
   branch. This is typically latest commit in the remote-tracking branch.
   e.g. `ec044d3e9b608ce275f02092f86810a3ba13834e`
* `REPO_RREV`: The remote revision.
   e.g. `master`
* `PREUPLOAD_COMMIT`: The commit that is currently being checked.
   e.g. `1f89dce0468448fa36f632d2fc52175cd6940a91`

## Placeholders

A few keywords are recognized to pass down settings.  These are **not**
environment variables, but are expanded inline.  Files with whitespace and
such will be expanded correctly via argument positions, so do not try to
force your own quote handling.

* `${PREUPLOAD_FILES}`: List of files to operate on.
* `${PREUPLOAD_COMMIT}`: Commit hash.
* `${PREUPLOAD_COMMIT_MESSAGE}`: Commit message.

Some variables are available to make it easier to handle OS differences.  These
are automatically expanded for you:

* `${REPO_ROOT}`: The absolute path of the root of the repo checkout.
* `${BUILD_OS}`: The string `darwin-x86` for macOS and the string `linux-x86`
  for Linux/x86.

## [Options]

This section allows for setting options that affect the overall behavior of the
pre-upload checks.  The following options are recognized:

* `ignore_merged_commits`: If set to `true`, the hooks will not run on commits
  that are merged.  Hooks will still run on the merge commit itself.

## [Hook Scripts]

This section allows for completely arbitrary hooks to run on a per-repo basis.

The key can be any name (as long as the syntax is valid), as can the program
that is executed. The key is used as the name of the hook for reporting purposes,
so it should be at least somewhat descriptive.

```
[Hook Scripts]
my_first_hook = program --gogog ${PREUPLOAD_FILES}
another_hook = funtimes --i-need "some space" ${PREUPLOAD_FILES}
some_fish = linter --ate-a-cat ${PREUPLOAD_FILES}
some_cat = formatter --cat-commit ${PREUPLOAD_COMMIT}
some_dog = tool --no-cat-in-commit-message ${PREUPLOAD_COMMIT_MESSAGE}
```

## [Builtin Hooks]

This section allows for turning on common/builtin hooks.  There are a bunch of
canned hooks already included geared towards AOSP style guidelines.

* `checkpatch`: Run commits through the Linux kernel's `checkpatch.pl` script.
* `clang_format`: Run git-clang-format against the commit. The default style is
  `file`.
* `commit_msg_bug_field`: Require a valid `Bug:` line.
* `commit_msg_changeid_field`: Require a valid `Change-Id:` Gerrit line.
* `commit_msg_test_field`: Require a `Test:` line.
* `cpplint`: Run through the cpplint tool (for C++ code).
* `gofmt`: Run Go code through `gofmt`.
* `google_java_format`: Run Java code through
  [`google-java-format`](https://github.com/google/google-java-format)
* `jsonlint`: Verify JSON code is sane.
* `pylint`: Run Python code through `pylint`.
* `xmllint`: Run XML code through `xmllint`.

Note: Builtin hooks tend to match specific filenames (e.g. `.json`).  If no
files match in a specific commit, then the hook will be skipped for that commit.

```
[Builtin Hooks]
# Turn on cpplint checking.
cpplint = true
# Turn off gofmt checking.
gofmt = false
```

## [Builtin Hooks Options]

Used to customize the behavior of specific `[Builtin Hooks]`.  Any arguments set
here will be passed directly to the linter in question.  This will completely
override any existing default options, so be sure to include everything you need
(especially `${PREUPLOAD_FILES}` -- see below).

Quoting is handled naturally.  i.e. use `"a b c"` to pass an argument with
whitespace.

See [Placeholders](#Placeholders) for variables you can expand automatically.

```
[Builtin Hooks Options]
# Pass more filter args to cpplint.
cpplint = --filter=-x ${PREUPLOAD_FILES}
```

## [Tool Paths]

Some builtin hooks need to call external executables to work correctly.  By
default it will call those tools from the user's `$PATH`, but the paths of those
executables can be overridden through `[Tool Paths]`.  This is helpful to
provide consistent behavior for developers across different OS and Linux
distros/versions.  The following tools are recognized:

* `clang-format`: used for the `clang_format` builtin hook.
* `cpplint`: used for the `cpplint` builtin hook.
* `git-clang-format`: used for the `clang_format` builtin hook.
* `gofmt`: used for the `gofmt` builtin hook.
* `google-java-format`: used for the `google_java_format` builtin hook.
* `google-java-format-diff`: used for the `google_java_format` builtin hook.
* `pylint`: used for the `pylint` builtin hook.

See [Placeholders](#Placeholders) for variables you can expand automatically.

```
[Tool Paths]
# Pass absolute paths.
clang-format = /usr/bin/clang-format
# Or paths relative to the top of the git project.
clang-format = prebuilts/bin/clang-format
# Or paths relative to the repo root.
clang-format = ${REPO_ROOT}/prebuilts/clang/host/${BUILD_OS}/clang-stable/bin/clang-format
```

# Hook Developers

These are notes for people updating the `pre-upload.py` hook itself:

* Don't worry about namespace collisions.  The `pre-upload.py` script is loaded
  and exec-ed in its own context.  The only entry-point that matters is `main`.
* New hooks can be added in `rh/hooks.py`.  Be sure to keep the list up-to-date
  with the documentation in this file.

## TODO/Limitations

* `pylint` should support per-repo pylintrc files.
* Some checkers operate on the files as they exist in the filesystem.  This is
  not easy to fix because the linters require not just the modified file but the
  entire repo in order to perform full checks.  e.g. `pylint` needs to know what
  other modules exist locally to verify their API.  We can support this case by
  doing a full checkout of the repo in a temp dir, but this can slow things down
  a lot.  Will need to consider a `PREUPLOAD.cfg` knob.
* We need to add `pylint` tool to the AOSP manifest and use that local copy
  instead of relying on the version that is in $PATH.
* Should make file extension filters configurable.  All hooks currently declare
  their own list of files like `.cc` and `.py` and `.xml`.
* Add more checkers.
  * `clang-check`: Runs static analyzers against code.
  * License checking (like require AOSP header).
  * Whitespace checking (trailing/tab mixing/etc...).
  * Long line checking.
  * Commit message checks (correct format/BUG/TEST/SOB tags/etc...).
  * Markdown (gitiles) validator.
  * Spell checker.